"Contemplating is receiving." (St. John of the Cross) What we receive in prayer is the Spirit, who makes all creation new, moment by moment. It is the Spirit who rebirths us within the caves of our hearts. The case is a metaphor for this silent withdrawal, this going away to be alone, to listen, to gestate the Spirit, to rebirth ourselves. The reborn self is the child of wisdom born in solitude.
Prayer is not a way to get what we want to happen, like the remote control that comes with the television set. I think prayer may be less about asking for the things we are attached to than it is about relinquishing our attachments in some way. It can take us beyond fear, which is an attachment, and beyond hope, which is another form of attachment. It can help us remember the nature of the world and the nature of life, not on an intellectual level but in a deep and experiential way. When we pray, we don't change the world, we change ourselves.